The Optomax 35mm f/2.8 was a wide-angle auto-diaphragm lens sold through UK camera shops in the 1970s, the same era and market that saw Optomax badge a range of budget Japanese-made optics. It gave film SLR owners a wider alternative to the standard 50mm lens without the cost of a first-party wide-angle.
Marked 'Auto' on the barrel, it was produced chiefly in M42 screw mount, with review coverage also noting a Pentax-fit version sold under the related Unitor and Promura badge-sharing arrangement. Build follows the all-metal, click-stop aperture ring pattern typical of the period, with a stop-down auto lever.
Reports from owners describe soft rendering wide open with contrast improving from around f/5.6, and mixed reliability in the auto-diaphragm coupling, with some samples eventually sticking open. It was regarded even at the time as a budget option rather than an alternative to Takumar or Zuiko wide-angles.
Copies sell cheaply on the used market, frequently under twenty pounds. Because the aperture-coupling mechanism is a known weak point, it is worth testing the auto lever action before buying and checking the diaphragm blades close evenly rather than hanging open.